GLib 2.39.1 introduces several GSettings fixes and improvements, among which we can mention that the GSettingsSchema API is more consistent and powerful, a new GSettingsSchemaKey API has been added to allow metadata access for keys, GSettingsSchemaSource received support for listing schemas within a source, gsettings list-schemas has been repaired, several GSettings now-redundant functionality has been deprecated, and two new GSettings APIs have been added (one for getting the default value of a key, and the other one for determining if the user has assigned a particular value to a key or not).
Moreover, GLib 2.39.1 brings several other new functionality to Applications, Actions, Appinfo, GDBus, GIO, and GRand components. Lots of Windows portability fixes have been introduced in this version, especially for MSVC. Also, numerous memory errors have been found and fixed in GLib itself and in the testcase, do to early testing of the upcoming GCleanup framework.